Process for the anionic polymerization of acrylic monomers and optionally of vinyl comonomers

ABSTRACT

A process for the polymerization of acrylic monomers and optionally of vinyl comonomers using (i) an initiator of formula (I): 
     
         R--M                                                       (I) 
    
     in which M denotes a metal selected from the group consisting of alkali metals and alkaline earth metals and R denotes a straight-chain or branched alkyl radical containing 2 to 6 carbon atoms or an aryl radical, and (ii) at least one non-nitrogenous macrocyclic complexing agent. 
     The polymerization process is used to make products of acrylic polymers having a narrow distribution of molecular masses.

This is a division of application Ser. No. 134,373, filed Dec. 18, 1987,now U.S. Pat. No. 4,826,941, dated May 2, 1989.

BACKGROUND OF THE INVENTION

The present invention relates to a process for the polymerization ofacrylic monomers and optionally of vinyl comonomers using an initiatorof formula (I):

    R--M                                                       (I)

in which M denotes a metal chosen from the group selected from alkalimetals and alkaline earth metals and R denotes a straight-chain orbranched alkyl radical containing 2 to 6 carbon atoms or an arylradical.

Processes for the polymerization of acrylic or methacrylic monomers,such as alkyl acrylates and methacrylates, as well as processes for thecopolymerization of acrylic or methacrylic monomers with vinylcomonomers, in the presence of various initiators, especially those offormula (I) given above are known. Examples of such initiators aresec-buthyllithium, napthalenesodium,1,4-disodio-1,1,4,4-tetraphenylbutane, diphenylmethylpotassium,diphenylmethylsodium, 1'-methylstyryllithium,1,1-diphenyl-3-methylpentyllithium and others, such as tertiaryalcoholates of lithium and compounds containing trimethylsilyl groups.

In polymerizing acrylic monomers and optionally non-acrylic comonomers,it is known to use additives or various catalysts, especiallycocatalysts or additives containing, for example, sources of fluoride,cyanide or acid ions or consisting of a Lewis acid. Finally, the use ofan alkali metal or alkaline earth metal salt of an inorganic acid isknown from European Patent Application No. 0,185,641.

On the other hand, French Patent No. 2,201,304 describes thepolymerization of vinyl monomers, especially of alkyl or cycloalkylacrylates and methacrylates, with anionic initiators in an organicsolvent medium and in the presence of a nitrogenous macroheterocycliccomplexing agent in a quantity that is at least equimolar relative tothe anionic initiator. This patent further describes the polymerizationof methyl methacrylate at -78° C. and +25° C. in benzene ortetrahydrofuran. The French certificate of addition No. 2,398,079,attached to this patent, describes a variation in which thepolymerization occurs in the absence of a solvent. In the case of methylmethacrylate, the polymerization is carried out at -40° C. and -80° C.respectively and leads to polymers having number average molecularmasses of 150,000 and 400,000, respectively.

SUMMARY OF THE INVENTION

It has now been discovered that it is advantageous to carry out thepolymerization of acrylic or methacrylic monomers, where appropriatewith vinyl comonomers, by polymerizing the acrylic or methacrylicmonomers in the presence of (i) initiator of formula (I) R--M and (ii) anon-nitrogenous macrocyclic complexing agent. In formula (I), M denotesa metal selected from the group consisting of alkali metals and alkalineearth metals and R denotes a straight chain or branched alkyl radicalcontaining 2 to 6 carbon atoms or an aryl radical

The present inventors have observed that the use of a non-nitrogenousmacrocyclic complexing agent in addition to the initiator of formula (I)R--M offers remarkable advantages. This complexing agent enables anarrower distribution of masses of the resulting polymers and copolymersand polymers having predetermined structures and masses to be prepared.

Without being bound by theory, it is believed that the use of anon-nitrogenous macrocyclic complexing agent in the process according tothe invention enables the reactivity of the initiator to be controlled.It is believed that the complexing agent advantageously reduces thereactivity of this initiator and makes it selective towards the doublebond of the acrylic or methacrylic monomer rather than towards the estergroup of this monomer.

The above and other features and advantages of the present inventionwill be made more apparent from the following description of thepreferred embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Examples of the non-nitrogenous macrocyclic complexing agents that canbe used as additives within the scope of the present invention includecyclic polyethers, which are also known as crown ethers, and cyclicpolythioethers, such as macrocyclic polyethers. The macrocyclic ring ofthe polyether preferably contains at least 14 carbon and oxygen atoms.Each oxygen atom of the ring is preferably separated from the otheroxygen atoms of the ring by two or three carbon atoms. Such macrocyclicpolyethers have already been described in U.S. Pat. No. 3,687,978.

More precise examples are in particular:

1,4,7,10,13,16-hexaoxacyclooctadecane,

2,3,11,12-dibenzo-1,4,7,10,13,16-hexaoxacyclooctadeca-1,11-diene,

2,3,12,13-dibenzo-1,4,11,14-tetraoxacycloeicosa-2,12- diene,

2,3,12,13,22,23-tribenzo-1,4,11,14,21,24-hexaoxacyclo-triaconta-2-12-22-triene,

2,2,7,7,12,12,17,17-octamethyl-21,22,23,24-tetraoxaquaterene,

2,3-benzo-1,4,7,10,13-pentaoxacyclopentadeca-2-ene,

2,3-(4'-t-butyl)-1,4,7,10,13,16-hexaoxacyclooctadeca-2-ene,

2,3,9,10-dibenzo-1,4,8,11-tetraoxacyclotetradeca-2,9-diene,

2,3,32,33-dibenzo-1,4,7,10,13,16,19,22,25,28,31,34,37,40,43,46,49,52,55,58-eicosaoxacyclohexaconta-2,32-diene,

2,3,16,17-dibenzo-1,4,15,18-tetraoxacyclooctacosa-2,16-diene,

2,6,13,17-tetraoxatricyclo[16.4.0.0⁷,12 ]docosane,

2,5,8,15,18,21-hexaoxatricyclo[20.4.0.0⁹,14 ]hexacosane,

2,5,12,15,18-pentaoxatricyclo[17.4.0.0⁶,11 ]tricosane,

2,6,13,16,19-pentaoxatricyclo[18.4.0.0.⁷,12 ] tetracosane,

9,10-benzo-2,5,8,11,14,17-hexaoxabicyclo[16.4.0]-docosa-9-ene,

2,3,9,10-dibenzo-1,4,8,11,14,16-hexaoxacyclooctadeca-2,9-diene,

2,3,11,12-dibenzo-1,4,7,10,13,16,18-heptaoxacycloeicosa-2,11-diene,

2,3,13,14-dibenzo-8-pentamethylene-1,4,7,9,12,15,18-heptaoxacycloeicosa-2,13-diene,

2,3,13,14-dibenzo-1,4,7,9,12,15,18,20-octaoxacyclodocosa-2,13-diene,

2,4-(1',8'-naphthylene)-1,5,8,11,14-pentaoxacyclohexadeca-2-ene.

Acrylic acid esters, methacrylic acid esters, dialkyl(meth)acrylamides,acrylonitrile, methacrylonitrile and their mixtures may advantageouslybe employed as acrylic monomers in the process according to theinvention. The acrylic monomer is preferably an alkyl methacrylatehaving an alkyl radical containing 1 to 18 carbon atoms. The alkylradical can be either substituted or unsubstituted. Examples of suchalkyl methacryates include methyl methacrylate, 2,2,2-trifluoroethylmethacrylate and butyl methacrylate. The alkyl methacrylate can alsopreferably be a secondary or tertiary alkyl acrylate having an alkylgroup containing from 3 to 8 carbon atoms. The alkyl group can be eithersubstituted or unsubstituted More particularly, such secondary ortertiary alkyl acrylates include isobutyl acrylate, tert-butyl acrylateand 2-ethylhexyl acrylate.

A vinyl comonomer such as, for example, butadiene, isoprene, styrene,vinylnaphthalene, 2-vinylpyridine, 4-vinylpyridine, alpha-methyl-styreneand tert-butylstyrene can be advantageously employed as a non-acryliccomonomer in the process according to the invention.

In the process according to the invention, the proportion ofnon-nitrogenous macrocyclic complexing agent relative to the initiatormay vary widely. For example, this quantity of the complexing agent maybe in a large excess relative to the molar quantity of the initiator.The quantity of the complexing agent may also be equal to or less thanthe molar quantity of the initiator. The complexing agent is preferablyin a molar proportion relative to the initiator which is at least equalto 0.5 and which may range up to approximately 5.

According to one embodiment of the process according to the invention,the polymerization reaction may be carried out in the presence, inaddition, of an alkali metal or alkaline earth metal salt. Preferably, ahalide or a boride of such a metal such as, for example, sodiumtetraphenylboron or lithium chloride is used. This salt may be employedin a molar proportion ranging up to approximately 2 relative to theinitiator.

The process according to the invention enables polymers and copolymershaving ends of chains functionalized by at least one group, such as acarboxylic group (COOH), to be prepared and block copolymers to beformed.

In the process according to the invention, the polymerization or thecopolymerization is preferably carried out in the absence of moistureand oxygen, and in the presence of at least one solvent. The solvent ispreferably chosen from aromatic solvents, such as benzene and toluene,tetrahydrofuran, diglyme, tetraglyme, orthoterphenyl, biphenyl, decalinor tetralin.

As regards the polymerization of copolymerization temperature, it mayvary between approximately -78° C. and 0° C.

The process according to the invention enables the preparation of awhole range of homopolymers and block copolymers generally having anumber average molecular mass of between approximatley 10,000 and300,000 and a polydispersity index generally between approximately 1.1and 4. The block copolymers include, as new polymers, particularly thefollowing: polymers containing at least one poly(2,2,2-trifluoroethylmethacrylate) block and, where appropriate, a polymer block of a monomerother than 2,2,2-trifluoroethylene methacrylate. These polymers aredefined by a polydispersity of between approximately 1.1 and 4 and by anumber average molecular weight of the poly(2,2,2-trifluoroethylmethacrylate) block preferably between approximately 10,000 and 300,000.

Such polymers are well suited for use in the production of photoresistsfor printed circuits. For such use, a solution is prepared at aconcentration between about 4% and 20% by weight of the polymer in aninert solvent such as ketone. This solution is then deposited onto asubstrate, such as silicium, before the solvent is evaporated to allowthe formation on the substrate of a polymer film having a thickness of,for example, in the range of about 0.2 to 2 microns. Other polymersformed by the process of the present invention include polymerscontaining at least one secondary alkyl acrylate polymer block, thealkyl group containing from 3 to 10 carbon atoms, and, whereappropriate, a polymer block of a monomer other than a secondary alkylacrylate. These polymers are defined by a polydispersity of betweenapproximately 1.1 and 4 and by a number average molecular weight of thepoly(secondary alkyl acrylate) block preferably between approximately10,000 and 100,000.

The process according to the invention is illustrated by the followingnon-limiting examples.

EXAMPLE 1

0.37 gram (0.75×10⁻³ mole) of2,3,11,12-dibenzo-1,4,7,10,13,16-hexaoxacyclooctadeca-1,11-dienemarketed by JANSSEN CHIMICA under the name "dibenzo-18-crown-6" isintroduced under a nitrogen atmosphere into a round-bottomed flask whichhas been dried beforehand.

150 ml of previously dried tetrahydrofuran are added and a 0.2 molarsolution of naphthalenesodium in tetrahydrofuran is added dropwise, withstirring, until a red color appears that persists. When this color isreached, 7.5 ml of the naphthalenesodium (1.5×10⁻³ mole) are added Themixture is cooled to a temperature of -78° C. using a mixture of acetoneand solid carbon dioxide and after 1/2 an hour, while still maintainingthe temperature at -78° C., 90 ml of a solution containing 0.057 mole of2-ehtylhexyl acrylate in tetrahydrofuran, which has previously beendried using triethylaluminum (1 ml of a 1 M solution in benzene) anddistilled, are added.

The reaction is stopped after 5 hours by adding 5 ml of methanol, afterwhich the solvent is removed. Poly(2-ethylhexyl acrylate) is obtainedwith a yield of 76%.

The analysis of the polymer by gel permeation chromatography gives thefollowing values:

M_(n) (number average molecular mass): 10,800

M_(w) /M_(n) (polydispersity index): 1.7

In the present example as well as in the following examples, thetetrahydrofuran was dried beforehand over sodium/benzophenone.

EXAMPLE 2

0.252 gram (0.0007 mole) of "dibenzo-18-crown-6" and 29 mg of lithiumchloride (0.0007 mole) are introduced under a nitrogen atmosphere into around-bottomed flask which has previously been dried 150 ml ofpreviously dried tetrahydrofuran are added dropwise with stirring, and a0.2 molar solution of naphthalenesodium in tetrahydrofuran is added,with stirring, until a red color appears that persists When this coloris reached, 3.75 ml of the naphthalenesodium solution (0.00075 mole) areadded.

The mixture is cooled to a temperature of -78° C. using a mixture ofacetone and solid carbon dioxide and after 1/2 hour, a tetrahydrofuransolution containing 5 g of 2-ethylhexyl acrylate (0.028 mole), which haspreviously been dried using triethylaluminum and distilled, is added.

After maintaining the temperature at -78° C. for 3 hours, during whichperiod the red color persists, the temperature is raised to -20° C. andmaintained at this level for 20 hours (a yellow color appears). Thereaction is then stopped by adding 5 ml of methanol, after which thesolvent is removed. 4.9 g of the polymer are obtained (yield: 98%).

The analysis of the polymer by gel permeation chromatography gives thefollowing values:

    M.sub.n =19,500  M.sub.w /M.sub.n =2.1

EXAMPLE 3

0.277 g (0.0008 mole) of "dibenzo-18-crown-6" is introduced, under anitrogen atmosphere, into a round-bottomed flask which has previouslybeen dried.

150 ml of previously dried tetrahydrofuran are added thereto and a 0.2molar solution of naphthalenesodium in tetrahydrofuran is addeddropwise, with stirring, until a red color appears that persists. Whenthis color is reached, 4 ml of the naphthalenesodium solution (0.0008mole) are added. The mixture is cooled to a temperature of -78° C. in amixture of acetone and solid carbon dioxide and after 1/2 an hour, whilestill maintaining the temperature at -78° C., 90 ml of a solutioncontaining 0.046 mole of 2,2,2-trifluoroethyl methacrylate intetrahydrofuran, which has previously been dried using triethyl aluminum(1 ml of a 1 M solution in benzene) and distilled, are added.

The reaction is stopped after 4 hours by adding 5 ml of methanol, afterwhich the solvent is removed. 7 g of the polymer are obtained to producea yield of 100%.

The analysis of the polymer by gel permeation chromatography gives thefollowing values:

    M.sub.n =26,000 M.sub.w /M.sub.n =1.23

EXAMPLE 4

The experiment in Example 3 is repeated with the following exception:before introducing the "dibenzo-18-crown-6", 29 mg of lithium chloride(0.0007 mole) are introduced into the round-bottomed flask. After 4hours of reaction, 7 grams of poly(2,2,2-trifluroethyl methacrylate) areobtained to produce a yield of 100%.

The analysis of the polymer by gel permeation chromatography gives thefollowing values:

    M.sub.n =96,000 M.sub.w /M.sub.n =1.22

EXAMPLE 5

10⁻³ mole of "dibenzo-18-crown-6" is introduced, under a nitrogenatmosphere, into a round-bottomed flask which has previously been dried.One liter of previously dried tetrahydrofuran and a living chain memberof poly(methylmethacrylate) initiated by diphenylmethylsodium (thelatter at a rate of 10⁻³ mole, as a molar solution in tetrahydrofuran)are added. The mixture is cooled to a temperature of -78° C. using amixture of acetone and solid carbon dioxide and a solution of 25 g of2,2,2-trifluoroethyl methacrylate in tetrahydrofuran, which haspreviously been dried and distilled, are then added. The reaction isstopped after 4 hours by adding methanol, after which the solvent isremoved. A copolymer containing methyl methacrylate/2,2,2-trifluoroethylmethacrylate blocks is obtained with a yield of 100%. The analysis ofthe copolymer by gel permeation chromatography gives the followingvalues:

    ______________________________________                                        M.sub.n                                                                             (total) = 33,000   M.sub.w /M.sub.n                                                                        = 1.33                                     M.sub.n                                                                             (methyl methacrylate block)  = 4,500                                    m.sub.n                                                                             (2,2,2-trifluoroethyl        = 28,500                                         methacrylate block                                                      ______________________________________                                    

EXAMPLE 6

5×10⁻³ mole of "dibenzo-18-crown-6" is introduced, under a nitrogenatmosphere, into a round-bottomed flask which has previously been dried.1 liter of previously dried tetrahydrofuran and 1.2×10⁻³ mole ofdiphenylmethylsodium as a molar solution in tetrahydrofuran are added.The mixture is cooled to a temperature of -78° C. using a mixture ofacetone and solid carbon dioxide and a solution of 150 g of2,2,2-trifluoroethyl methacrylate in tetrahydrofuran, which haspreviously been dried and distilled, is then added. The reaction isstopped after 3 hours by adding methanol, after which the solvent isremoved. The polymer is obtained with a yield of 90%.

The analysis of the polymer by gel permeation chromatography gives thefollowing values:

    M.sub.n =185,000 M.sub.w /M.sub.n =1.33

Such a polymer is well suited for the production of photoresists forprinted circuits.

EXAMPLE 7

0.2×10⁻³ mole of "dibenzo-18-crown-6" is introduced, under a nitrogenatmosphere, into a round-bottomed flask which has previously been dried120 ml of previously dried tetrahydrofuran and 0.2×10⁻³ mole ofnaphtahlenesodium as a molar solution in tetrahydrofuran are added Themixture is cooled to a temperature of -78° C. using a mixture of acetoneand solid carbon dioxide and a solution of 5 g of isobutyl acrylate intetrahydrofuran, which has previously been dried and distilled, is thenadded. The reaction is stopped after 4 hours by adding methanol, afterwhich the solvent is removed. Poly(isobutyl acrylate) is obtained with ayield of 90%.

The analysis of the polymer by gel permeation chromatography gives thefollowing values:

    M.sub.n =37,000 M.sub.w /M.sub.n =2.0

EXAMPLE 8

The experiment in Example 7 is repeated with the following exception:before introducing the "dibenzo-18-crown-6", 0.4×10⁻³ mole of sodiumtetraphenylboron is introduced into the round-bottomed flask. After 4hours of reaction, the poly(isobutyl acrylate) is obtained with a yieldof 100%.

The analysis of the polymer by gel permeation chromatography gives thefollowing values:

    M.sub.n =36,000 M.sub.w /M.sub.n =3.6

EXAMPLE 9

10⁻³ mole of "dibenzo-18-crown-6" is introduced, under a nitrogenatmosphere, into a round-bottomed flask which has previously been dried.400 ml of previously dried tetrahydrofuran and 0.2×10⁻³ mole ofnaphthalenesodium as a molar solution in tetrahydrofuran are added. Themixture is cooled to a temperature of -78° C. using a mixture of acetoneand solid carbon dioxide and a solution of 5 g of isobutyl acrylate intetrahydrofuran, which has previously been dried and distilled, is thenadded. The reaction is stopped by adding methanol, after which thesolvent is removed. Poly(isobutyl acrylate) is obtained with a yield of81%.

The analysis of the polymer by gel permeation chromatography gives thefollowing values:

    M.sub.n =23,000 M.sub.w /M.sub.n =1.5

EXAMPLE 10

0.2×10⁻³ mole of lithium chloride and 0.4×10⁻³ mole of"dibenzo-18-crown-6" are introduced, under a nitrogen atmosphere, into around-bottomed flask which has previously been dried. 100 ml ofpreviously dried tetrahydrofuran and 0.2×10⁻³ mole of naphthalenesodiumas a molar solution in tetrahydrofuran are added. The mixture is cooledto a temperature of -78° C. using a mixture of acetone and solid carbondioxide and a solution of 5 g of methacrylonitrile in tetrahydrofuran,which has previously been dried and distilled, is then added. Thereaction is stopped after 1 hour by adding methanol, after which thesolvent is removed. The polymer is obtained with a yield of 62%.

What is claimed is:
 1. A polymer comprising a homopolymer of2,2,2-trifluorethyl methacrylate or a copolymer comprising at least onepoly(2,2,2-tri-fluoroethyl methacrylate) block, said homopolymer orcopolymer having a polydispersity between 1.1 and 4 and a number averagemolecular weight of between 10,000 and 300,000.
 2. The polymer asclaimed in claim 1, further comprising a monomer other than2,2,2-trifluoroethyl methacrylate.
 3. A photoresist for printedcircuits, containing at least one polymer as claimed in claim
 1. 4. Thephotoresist for printed circuits as claimed in claim 3, wherein thepolymer is in the form of a film having a thickness in the range of 0.2to 2 microns.
 5. A polymer comprising a homopolymer of a secondary alkylacrylate monomer or a copolymer comprising at least one secondary alkylacrylate polymer block, said alkyl group containing from 3 to 10 carbonatoms and having a polydispersity of between approximately 1.1 and 4 anda number average molecular weight of the homopolymer or poly(secondaryalkyl acrylate) block of between 10,000 and 100,000.
 6. The polymer asclaimed in claim 5, further comprising a polymer block of a monomerother than a secondary alkyl acrylate.